feat(osaka): add eip-7939 count leading zeros opcode (#1275)

* feat(vm): add eip-7939 count leading zeros opcode.

* Update src/ethereum/osaka/vm/instructions/bitwise.py

Co-authored-by: Guruprasad Kamath <[email protected]>

* code formatting

---------

Co-authored-by: Guruprasad Kamath <[email protected]>
Co-authored-by: Guruprasad Kamath <[email protected]>

Author: 2 people

src/ethereum/osaka/vm/instructions/__init__.py

@@ -65,6 +65,7 @@ class Ops(enum.Enum):
     SHL = 0x1B
     SHR = 0x1C
     SAR = 0x1D
+    CLZ = 0x1E
 
     # Keccak Op
     KECCAK = 0x20
@@ -241,6 +242,7 @@ class Ops(enum.Enum):
     Ops.SHL: bitwise_instructions.bitwise_shl,
     Ops.SHR: bitwise_instructions.bitwise_shr,
     Ops.SAR: bitwise_instructions.bitwise_sar,
+    Ops.CLZ: bitwise_instructions.count_leading_zeros,
     Ops.KECCAK: keccak_instructions.keccak,
     Ops.SLOAD: storage_instructions.sload,
     Ops.BLOCKHASH: block_instructions.block_hash,

src/ethereum/osaka/vm/instructions/bitwise.py

@@ -238,3 +238,31 @@ def bitwise_sar(evm: Evm) -> None:
 
     # PROGRAM COUNTER
     evm.pc += Uint(1)
+
+
+def count_leading_zeros(evm: Evm) -> None:
+    """
+    Count the number of leading zero bits in a 256-bit word.
+
+    Pops one value from the stack and pushes the number of leading zero bits.
+    If the input is zero, pushes 256.
+
+    Parameters
+    ----------
+    evm :
+        The current EVM frame.
+    """
+    # STACK
+    x = pop(evm.stack)
+
+    # GAS
+    charge_gas(evm, GAS_VERY_LOW)
+
+    # OPERATION
+    bit_length = U256(x.bit_length())
+    result = U256(256) - bit_length
+
+    push(evm.stack, result)
+
+    # PROGRAM COUNTER
+    evm.pc += Uint(1)

whitelist.txt

@@ -475,3 +475,5 @@ eoa
 blockchain
 listdir
 precompiles
+
+CLZ